Start out in pushup position with one knee bent. Keep your hands on the ground and push off with your feet so you alternate foot placement (run in place). Be sure to keep your back straight, not arched. Resist side-to-side and up-and-down hip movement by contracting abdominal muscles.
Start out with slow controlled strides and work toward increasing speed without hip movement.
2 sets of 10 second controlled strides.
Over time work up to 30, 45, or 60 seconds.
Also progression can be made by increasing the number of reps over the time.